Tritium is a radioactive isotope of hydrogen that is sometimes used in the production of nuclear weapons. An ionization chamber, which can be used for the detection or measurement of ionizing radiation, may be employed in order to conduct a tritium measurement. Tritium flowing through an ionization chamber emits beta particles that generate a current proportional to the tritium radioactivity. This current can be measured with the use of an electrometer to thus ascertain tritium activity. This current is generally in the 1×10−15 (femto) amp to 1×10−6 (micro) amp range.
Certain challenges exist in obtaining accurate measurements of these low currents. For example, the distance between the ionization chamber and the electrometer can be over 100 or 150 feet, and voltages utilized in the 500 to 1000 volt range require that the ionization chamber be grounded to earth ground. This grounding along with long cable lengths and low currents require a special pre-amplifier circuit be employed in the electrometer. Electrometers on the market today suffer from problems such as ground loops, high background currents, erroneous date spikes when changing ranges, alternating current common mode rejection, and susceptibility to electromagnetic interference that includes radio frequency and magnetic fields. Certain electrometers are not capable of being used with different ionization chamber designs that are required by gas pressure, gas type, and range.
Facilities that handle substances such at tritium require routine maintenance checks to ensure all associated equipment is properly functioning. For example, at some Department of Energy facilities monthly calibration and alarm checks must be performed in order to ensure operational readiness. Electrometers in use today do not have a fail safe self monitoring capability and thus require labor intensive monitoring.
Variations in temperature can introduce errors into the final reading when measuring low currents. Electronic components such as amplifiers, transistors, and resistors require time in order to thermally stabilize before an electrometer can accurately measure currents in the 1×10−14 to 1×10−15 amp range. Existing electrometers do not provide an indication to the user as to when the electrometer has thermally stabilized and is thus capable of accurately measuring low levels of current. Further, electrometers are only capable of measuring into the low 1×10−14 amp range when used to measure current in an industrial environment such as during the measurement of tritium in an ionization chamber.
Accordingly, there remains room for variation and improvement within the art.